Welcome and time to have some fun!
1. Totally your call on color scheme. A full black theater is ideal for video performance, but feels pretty oppressive to most folks during anytime the video isn't on. I personally would not really like an all black room. I just did my temp theater here in brown, and like it quite a bit.
2. No real issue between spraying or rolling. Just make sure you use a flat paint, no glossy paint.
3. Yes on ceiling, you don't want to have the walls dark and the ceiling white, that will look odd. You should pick a complimentary color though, don't use the exact same color as your walls it will feel overwhelming. I would paint the doors yes, or they will stick out as big white rectangles.
4. Light controlled simply means you can control the amount of light in the room.
5. Screen color is best determined by matching to your projector. The 8350 is bright and has good contrast so a gray screen probably isn't required.
6. Congratulations on having a wife that wants it bigger.
If you have been using a 135" for a while now and are used to it (and like it), then just stick with what you personally enjoy. Yes there is technically a decrease in how bright the image will appear going from 122 to 135, but since you are already used to that image size, I'd stick with that.